// select.js — which nodes and edges are selected.
//
// Kept apart from the document so selection never lands in the undo stack or
// on disk: undoing an edit should restore geometry, not re-select whatever
// happened to be highlighted at the time.
window.Canvas = window.Canvas || {};

Canvas.Select = (function () {
    var nodes = {};
    var edges = {};
    var listeners = [];

    function emit() {
        for (var i = 0; i < listeners.length; i++) listeners[i]();
    }

    function keys(obj) { return Object.keys(obj); }

    return {
        nodes: function () { return keys(nodes); },
        edges: function () { return keys(edges); },
        hasNode: function (id) { return !!nodes[id]; },
        hasEdge: function (id) { return !!edges[id]; },
        isEmpty: function () { return !keys(nodes).length && !keys(edges).length; },
        count: function () { return keys(nodes).length + keys(edges).length; },

        set: function (nodeIds, edgeIds) {
            nodes = {};
            edges = {};
            (nodeIds || []).forEach(function (id) { nodes[id] = true; });
            (edgeIds || []).forEach(function (id) { edges[id] = true; });
            emit();
        },

        addNode: function (id) {
            if (nodes[id]) return;
            nodes[id] = true;
            emit();
        },

        toggleNode: function (id) {
            if (nodes[id]) delete nodes[id]; else nodes[id] = true;
            emit();
        },

        toggleEdge: function (id) {
            if (edges[id]) delete edges[id]; else edges[id] = true;
            emit();
        },

        clear: function () {
            if (!keys(nodes).length && !keys(edges).length) return;
            nodes = {};
            edges = {};
            emit();
        },

        // prune drops ids that no longer exist. Called after undo/redo, where
        // the document can lose nodes the selection still refers to.
        prune: function (doc) {
            var changed = false;
            var live = {};
            doc.nodes.forEach(function (n) { live[n.id] = true; });
            keys(nodes).forEach(function (id) {
                if (!live[id]) { delete nodes[id]; changed = true; }
            });
            var liveEdges = {};
            doc.edges.forEach(function (e) { liveEdges[e.id] = true; });
            keys(edges).forEach(function (id) {
                if (!liveEdges[id]) { delete edges[id]; changed = true; }
            });
            if (changed) emit();
        },

        onChange: function (fn) { listeners.push(fn); }
    };
})();